Quite often even venerable developers of electronics poorly understand the electromagnetic equipment and are not able to choose competently design and to make calculation of the IVP electromagnetic components. It is not surprising because presently electronics covers quite wide field of knowledge and the expert who has got education in narrow area is forced to make in practice decisions in adjacent areas. Sharply this problem concerns the fans who do not have absolutely vocational education.
1. Remove ratios which you will use further. Conduct calculation for the throttle working with bias. For use even of very simplified formulas it is necessary to understand their structure accurately. Traditionally in classical sources on miscellaneous assessment of dimensions of magnetic conductor is made for throttles and transformers. For the first the volume of the core is equal to the work of average length of magnetic force line on core sections on, Sc*1c, for the transformer - the work of the area of window with So winding on the area of cut of the Sc core. Throttles which work with bias have non-magnetic gap which has magnetic resistance in hundreds and thousands of times above the magnetic resistance of magnetic conductor. Taking it in attention, ignore the magnetic resistance of the core, consider it zero, and evaluate throttle dimensions through Sc*So, also as the transformer.
2. Define flux linkage of throttle winding, for the chosen induction of B: Ψ=W*B*Sc*Kc*10-4, or Ψ=0.1*BJ*Sc*So*Kc*Ko/I.Найдите inductance of throttle, proceeding from two previous formulas: L=0.01*Sc*So*B*J*Kc*Ko/I^2 and also Sc*So value for its core: Sc*So=100*L*I^2 / (B*J*Kc*Ko). The choice of values J, B, Kc, Ko undertakes from similar to the recommendation for transformers "S.G. Bunin, L.P. Yaylenko. The reference book by the radio fan - korotkovolnovik". Rgab equate dimensional power to Sc*So. Current density for aluminum wire should be reduced by 1.6 times. For example: construction of adjustable welding source. It eats from single-phase network of 220B 50 Hz, the welding current is regulated ranging from Imin = 50 A to Imaks = 150A by the operated thyristor rectifier, FL (frequency of loading) = 40%. In order that the welding arch did not die away in tension pauses, the throttle has to support current at the certain level, not below Ist = 10A, at the maximum angle of regulation and minimum current. The minimum inductance of throttle is equal: Lmin =0.25*ud / (F * (Imin-Ist)) =0.25 * (18+0.05*imin) / (F * (Imin-Ist)) = 0.25 * (18+0.05*50)/(50*(50-10)) =2.56mgn.
3. Reel up it on the E core from steel 3411. Previously choose J=5А/мм^2 (taking into account the set PN), V=1.3Tl, Ko=0.35, Kc=0.95. Determine by formula: Sc*So=100*2.56e-3*150^2 / (1.3*5*0.95*0.35) =2665см^4. Use for throttle two ShL40h80 cores (Sc*Kc=30см^2, So=40см^2). Define quantity of rounds: W=100*40*0.35*5/150=46 rounds of wire, which section Spr =Iмакс/J=150/5=30мм^2. Define non-magnetic gap: δ=150*46 / (796*1.3) =6.7 mm. Define the resulting inductance: L=1.25*10e-7*60*46^2/6.7=2.37мГн. It almost corresponds to set value of the minimum inductance, but in practice it will matter slightly above as the inductance of dispersion is not considered.